1. Technical Field
The present invention relates to a liquid crystal display device and to an electronic apparatus.
2. Related Art
Reflection-type liquid crystal display devices, which have an advantage of low power consumption because of not having a light source, such as a backlight and the like, have been generally employed for additional display units to various portable electronic apparatuses and the like. However, since the reflection-type liquid crystal display devices display images using external light such as natural light, for example, sunlight or illumination light, there is a problem in that it is difficult for users to view displayed characters and the like on display units in a dark place.
In order to overcome such a disadvantage, a liquid crystal display device has been widely used to allow images to be viewed by observers using the external light in a light place like the general reflection-type liquid crystal display devices and using an internal light source such as a backlight or the like in a dark place. That is, this liquid crystal display device employs both the reflective and transmissive display modes, and thus by changing the display mode between the reflective and transmissive display modes depending on ambient brightness, it is possible to reduce power consumption and allows images to be clearly viewed even in dark places. Accordingly, the external light contributes to display of images in the reflective display mode while light emitted from an illumination unit such as the backlight (hereinafter, referred to as ‘illumination light’) contributes to display of images in the transmissive display mode.
Hereinafter, in the specification, such a liquid crystal display device is referred to as ‘a transflective liquid crystal display device’.
In general, the transflective liquid crystal display device has a liquid crystal display panel including a pair of substrates and liquid crystal interposed between the pair of substrates, and an illumination unit provided at a side opposite to a side from which the liquid crystal display panel is observed and radiating light onto a substrate surface of the liquid crystal display panel. In addition, a reflective layer having a plurality of openings (transflective layer) is provided in a substrate located at the side opposite to the side from which the liquid crystal display panel is observed.
In addition, recently, with the development of portable electronic apparatuses or OA apparatuses, color liquid crystal display has been required and color display has been required for electronic apparatuses having the transflective liquid crystal display device.
As a transflective liquid crystal display device meeting such a requirement, a transflective liquid crystal display device having color filters has been suggested. In such a transflective liquid crystal display device, in a reflection mode, external light incident on the liquid crystal display device passes through the color filters, is then reflected by a reflecting plate, and then again passes through the color filters. In addition, in a transmission mode, light emitted from a backlight passes through the color filters. In addition, the same color filters are used in both the reflection mode and the transmission mode.
However, in the transflective liquid crystal display device, only one of the black and white display and the color display can be performed in either the reflection display mode or the transmission display mode. For example, in the case of a liquid crystal display device for use in a portable telephone, there is a problem in the lack of versatility, as in the case in which the black and white display can be performed in a standby mode (reflection display when the backlight is turned off) and the color display can be performed in an operation mode (transmission display when the backlight is turned on). In addition, in order to improve brightness and visibility of display, the amount of power supply of the backlight has to increase or the brightness and visibility of one of the reflection display and the transmission display must be sacrificed. Accordingly, there is a strong demand for a liquid crystal display device with improved brightness and high visibility without increasing the cost.
Accordingly, there has been proposed a liquid crystal display device including a reflection film having transmission holes through which light substantially passes and color filters constructed by colored layers provided in a region corresponding to the transmission holes on a substrate (for example, see Japanese Unexamined Patent Application Publication No. 2003-43239). The invention can provide a liquid crystal display device allowing the black and white display in the reflection display mode and the color display in the transmission display mode with improved brightness or visibility of display in the transmission display mode or the reflection display mode without increasing the cost.
Each of the color filters of the liquid crystal display device includes a reflective layer reflecting incident light such as external light, a transmission portion through which illumination light passes, and sub-pixels formed on the transmission portion and having respective colored layers of red (R), green (G), and blue (B). In addition, transmission portions provided on reflective layers of the sub-pixels have the same area for all sub-pixels corresponding to red (R), green (G) and blue (B), that is, the same aperture.
Accordingly, in the liquid crystal display device disclosed in Japanese Unexamined Patent Application Publication No. 2003-43239, the areas of the reflective layers of the sub-pixels corresponding to red (R), green (G), and blue (B) become equal. For this reason, when a display mode is switched from the transmission mode to the reflection mode, for example, if images such as characters of a primary color (one of R, G and B colors) are displayed on a background image of a primary color (one of R, G and B colors), the reflectance to the incident light for each of the sub-pixels having different colors is equal. As a result, no difference occurs in brightness at a boundary between the background image and the character images, and accordingly, it is difficult to distinguish the boundary between the background image and the character images, which results in deterioration of visibility for an observer in the reflection mode.